It is impossible to discern acceleration from a relative frame of reference. This is called The Equivalence Principle. You might want to study it as it is one of the most basic principles in physics.
I am familiar with the equivalence principle. It states that in any small region of space-time, the effects of a gravitational field are indistinguishable from those of an appropriate acceleration of the frame of reference.
Because of this principle, if I was unable to see (if I were in a closed box) and it were in free-fall, I would not be able to tell if I was experiencing the affects of free-fall or the affects of zero-gravity.
Similarly, if I were approaching the Earth at an acceleration of 9.81m/s^2, I would not be able to tell if it was gravity working on me or in the case that Earth had no gravity that the Earth was accelerating towards me at the same rate as gravity. (The impact with the Earth would be the same).
The difference between the principle and the idea that the Earth is accelerating in an upward direction is the direction of the forces on our bodies. With gravity, I would be falling to the Earth, whereas with an accelerating Earth, a force pushing up on us. In the case of Gravity, when on the ground, there is no acceleration. In the case an an accelerating Earth, there is an acceleration 'upwards' in which case inertia would work in opposition.
But we digress...
More important than the affects of inertia if certain situations were true is the evidence that the Earth is accelerating in an 'upward' direction. Without evidence, the idea, no matter how good it sounds, is merely a guess.